1. Field of the Invention
The present invention relates to a process for producing benzylsodium as an intermediate for the production of phenylacetic acid and derivatives thereof.
The present invention also relates to a process for producing phenylacetic acid, salts or esters thereof which are useful as precursors for the synthesis of penicillin G, perfume additives and as intermediates for dyes, medicines, agricultural chemicals and the like. More particularly, it relates to a process for producing phenylacetic acid, salts or esters thereof in high yield from chlorotoluene as a starting material and by a previously unknown rearrangement. Heretofore, phenylacetic acid has been produced by reacting chlorobenzene with sodium at a temperature less than 40.degree. C to yield phenylsodium, and then reacting toluene with phenylsodium to yield benzylsodium and reacting carbon dioxide with the benzylsodium to yield sodium phenylacetate. The sodium phenylacetate is then contacted with a mineral acid to yield phenylacetic acid as shown in the following reaction sequence. (Industrial and Engineering Chemistry 46, Page 539, 1954). ##STR1## However, the reaction temperature of the conventional procedure which uses the chlorobenzene as the starting material, is hard to control in the step in which chlorobenzene is reacted with sodium. The difficulty in controlling the temperature makes it difficult to control the formation of biphenyl by-product. In other words, the reaction between chlorobenzene and sodium is not smooth at temperatures less than 30.degree. C. If the temperature is higher than 40.degree. C, a side reaction occurs between phenyl sodium and the chlorobenzene starting material which produces biphenyl as follows. ##STR2##
Thus, in order to inhibit the formation of the by-product biphenyl, it is necessary to control the reaction temperature in a range of 31.degree. C to 40.degree. C.
The reaction of chlorobenzene with sodium is a severe exothermic reaction, and consequently, it is hard to control the reaction temperature and prevent the formation of by-product biphenyl. Moreover, the conventional method of using chlorobenzene has the disadvantage in that large amounts of by-product benzene are formed. In the process, phenylsodium obtained by the reaction of chlorobenzene with sodium is reacted with toluene to yield benzylsodium. In the reaction of phenylsodium with toluene, benzene is necessarily formed as a coproduct with benzylsodium. Thus, benzene is unavoidably formed as a by-product in the conventional process.
A need, therefore, continues to exist for a method by which benzylsodium can be prepared as an intermediate for the synthesis of phenylacetic acid.